This invention is based on an indirect manual transmission for motorcycles having cross-country mobility and, more particularly to an indirect manual transmission for a motor vehicle including an input shaft and a secondary shaft which is driven by this input shaft and whose gear wheels are disposed as loose wheels on the respective shaft partially in a non-rotatable and partially in a rotatable manner, and also including a shiftable cross-country reduction stage which is connected behind and which is integrated in the transmission unit.
From German Patent document DE 30 06 811 A1, a manual transmission for motor vehicles is known. The manual transmission is constructed as an indirect manual transmission with an input shaft, which is arranged in parallel, and with a secondary shaft. In this case, the gear wheels of the input shaft are non-rotatably connected with the shaft, while the gear wheels of the secondary shaft are rotatably disposed on this secondary shaft as loose wheels or control gears and can be shifted into a non-rotatable connection by way of shift dogs. A reduction stage or reduction gear is connected behind the manual transmission. The countershaft of this reduction gear is arranged in parallel to the secondary shaft of the transmission. The shifting of the two stages of the reduction gear takes place by way of a shift dog arranged on the countershaft. As a result of such an arrangement of the reduction gear or of the reduction stage, the manual transmission becomes relatively wide. In addition, this type of an arrangement of three parallel shafts requires considerable bearing expenditures.
From German Patent document DE 34 28 451 A1, an indirect manual transmission is known in the case of which the reduction gear or the reduction stage is constructed as a front-mounted splitter unit on the input side of the manual transmission. This front-mounted reduction gear has two transmission ranges; one transmission range for high speeds and one transmission range for low speeds. In this case, the transmission range for high speeds can be shifted by way of a hydraulic clutch, while the transmission range for the low speed can be shifted by way of a one-way clutch.
There is therefore needed an indirect manual transmission for vehicles having cross-country mobility constructed in such a manner that this manual transmission has a compact construction, while allowing the main transmission as well as the reduction gear to be shifted in an easy manner.
These needs are met according to the present invention by an indirect manual transmission for a motor vehicle including an input shaft and a secondary shaft which is driven by this input shaft and whose gear wheels are disposed as loose wheels on the respective shaft partially in a non-rotatable and partially in a rotatable manner, and also including a shiftable cross-country reduction stage which is connected behind and which is integrated in the transmission unit. A loose wheel of the input shaft is constructed as a twin gear wheel and can be operated as a countershaft of the cross-country reduction stage.
If, in the case of an indirect manual transmission, one of the loose wheels on the input shaft is constructed as a twin wheel, this twin wheel can be utilized as a countershaft for the reduction gear. This permits a coaxial arrangement of the reduction gear so that the size of the transmission (cross-section perpendicular to the longitudinal axis of the transmission) does not increase or only insignificantly increases with respect to a manual transmission without any reduction stage. At the same time, in comparison to a conventional manual transmission with a rear-mounted reduction stage, this type of a transmission is shorter and is only slightly longer than a manual transmission without a reduction stage because the additional length is minimized by the "double utilization" of a loose wheel of the manual transmission. In this case, the shifting of the reduction stage may take place using a conventional gear shift sleeve. A synchronization of the shifting operation is easily made possible.
In an advantageous embodiment of the invention, the loose wheel constructed as a twin gear wheel is assigned to one of the upper speeds of the manual transmission, particularly to the highest speed. This results in favorable circumferential dimensions for the reduction stage. Further, the rotational speeds and torques occurring during the operation can be controlled without requiring an increase in the gear wheel width of the corresponding loose wheel beyond the conventional measurements. In contrast to the gear wheels of the lower speeds, the gear wheels of the upper or of the highest speed are designed for high continuous loads which also permits a continuous operation of the reduction stage without any excessive widening of the gear wheel.
An indirect manual transmission which is constructed in this manner is particularly suitable for installation in a longitudinal direction of the motor vehicle in conjunction with an engine which is also mounted in the longitudinal direction. This engine can be arranged in front of the front axle of the motor vehicle and therefore permits a relatively low height for the engine compartment. In this case, the transmission can advantageously be arranged in the area of the front axle so that a front wheel drive can be driven directly in the area of the transmission.
For the all-wheel drive of the motor vehicle, the transmission can very advantageously have a very compact construction if the pinion shaft of one of the axle drives (particularly of the front axle drive) is guided in the secondary shaft of the transmission constructed as a hollow shaft.
If the output shaft of the reduction gear or of the reduction stage is constructed as a hollow shaft through whose bore the pinion shaft of an axle drive (particularly of the front axle drive) is guided, an all-wheel drive can be represented in a particularly compact construction without an excessive increase in the length and the circumference of the transmission. For the all-wheel drive of the motor vehicle, it is advantageous to provide a center differential with a coaxial output to the front and the rear axle in the power flux behind the reduction gear. This center differential can advantageously be integrated in the transmission case. It may be constructed, for example, as a self-locking differential of the torsen construction, as a multi-disk limited-slip differential or as a visco-clutch.
The overall length of the indirect manual transmission may be again shortened if a connection clutch is arranged instead of the center differential in the power flux behind the reduction gear, by means of which connection clutch one of the two axle drives can be connected to a permanently driven axle drive.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.